Device for interrupting non-short circuit currents only, in particular disconnector or earthing switch

ABSTRACT

The present invention relates to a device for interrupting non-short circuit currents only, and in particular relates to a disconnector, more particularly high voltage disconnector, or to an earthing switch, more particularly make-proof earthing switch, and further relates to a low voltage circuit breaker. The device comprises at least two contacts movable in relation to each other between a closed state and an open state and defining an arcing region, in which an arc is generated during a current interrupting operation and in which an arc-quenching medium comprising an organofluorine compound is present. According to the application, a counter-arcing component is allocated to the arcing region, the counter-arcing component being designed for counteracting the generation of an arc and/or being designed for supporting the extinction of an arc.

The present invention relates to a device for interrupting nonshort-circuit currents only, in particular to a disconnector, moreparticularly a high voltage disconnector, or an earthing switch, moreparticularly a make-proof earthing switch, as well as to a mediumvoltage or high voltage gas-insulated switchgear (GIS) comprising such adevice. The present invention further relates to a low voltage circuitbreaker.

Dielectric insulation media in liquid or gaseous state areconventionally applied for the insulation of an electrically conductivepart in a wide variety of apparatuses, and in particular also in GIS orcomponents thereof.

In medium or high voltage metal-encapsulated switchgears, for example,the electrically conductive part is arranged in a gas-tight housing,which defines an insulating space, said insulation space comprising aninsulation gas and separating the housing from the electricallyconductive part without allowing electrical currents to pass through theinsulation space.

For interrupting the current in e.g. high voltage switch-gears, theinsulating medium further functions as an arc-quenching medium (orarc-extinction medium). This is e.g. also the case in a disconnector orin an earthing switch, in which the arc generated during currentinterruption is extinguished under free-burning conditions, meaning thatthe arc-quenching medium is not actively blown towards the arc.

In conventional gas-insulated switchgears, sulphur hexa-fluoride (SF₆)is typically used as insulation medium and/or arc-quenching medium,respectively.

Recently, the use of organofluorine compounds in an insulation mediumhas been suggested as a substitute for conventional insulation media.Specifically, WO-A-2010/142346 discloses a dielectric insulation mediumcomprising a fluoroketone containing from 4 to 12 carbon atoms. Further,WO-A-2012/080246 discloses a fluoroketone containing exactly carbonatoms (hereinafter referred to as “C5K”) in a mixture with a dielectricinsulation gas component different from said C5K to be particularlyadvantageous. The fluoroketones disclosed in WO-A-2010/142346 andWO-A-2012/080246 have been shown to have high insulation capabilities,in particular a high dielectric strength, as well as high arc extinctioncapabilities. At the same time, they have a very low Global WarmingPotential (GWP) and very low toxicity.

Notwithstanding the above-mentioned excellent properties of afluoroketone-containing insulation gas, it has unexpectedly been foundthat in a device designed for interrupting non-short circuit currentsonly, specifically in a disconnector or an earthing switch of aconventional design, interruption of even low currents could fail whenusing a fluoroketone-containing arc-quenching medium. This is due to thefluoroketone being present in relatively low concentrations in thesedevices, which goes along with relatively poor thermodynamic andtransport properties and thus relatively poor cooling efficiency. Theproblem particularly applies to arc-quenching media that besides theorganofluorine compound comprise a carrier or background gas, typicallyair or an air component. For example, tests have shown that an earthingswitch, which repeatedly interrupts an inductive current of 80 A inseveral tens of milliseconds or less in SF₆, failed to interrupt evenlower currents in air and CO₂ even after more than half a second ofarcing, even though a correspondingly larger gap between the contactshas then been achieved.

Thus, the favourable properties inherent to SF₆, which allow efficientextinction of the arc at current-zero also at unblown conditions andwhich further ensure that the arc does not reignite, are not inherent tosuch gas mixtures containing organofluorine compounds.

The problem of the present invention is to provide an improved devicefor interrupting non-short circuit currents only, particularly adisconnector or an earthing switch, by using an arc-quenching mediumcontaining an organofluorine compound, said device allowing at the sametime a very reliable current interruption. This problem is solved by thesubject matter of claim 1. Embodiments are defined in dependent claimsor claim combinations and in the description in conjunction with thedrawings.

According to claim 1, the present invention relates to a device forinterrupting non-short circuit currents only. Respective devices of thestate of the art are designed such that the arc generated duringinterruption is conventionally extinguished by SF₆ under unblownconditions, i.e. without actively inducing a gas flow of SF₆ asarc-quenching medium.

The device of the present invention comprises at least two contactsmovable in relation to each other between a closed state and an openstate and defining an arcing region, in which an arc is generated duringa current interrupting operation and in which an arc-quenching mediumcomprising an organofluorine compound is present.

According to the invention, a counter-arcing component is allocated tothe arcing region, said counter-arcing component being designed forcounteracting the generation of an arc and/or for supporting theextinction of an arc.

As mentioned, the device of the present invention is designed forinterrupting non-short circuit currents only. Particularly herein, theterm “short-circuit currents”, as opposed to non-short circuit currents,is thereby defined as currents that are established in the first,transient phase of up to approximately 3 seconds after the point intime, when from a grid operated under high voltage the parts under highvoltage get connected to ground. According to this definition, the term“non short-circuit currents” relates to any currents not falling underthe definition of “short-circuit currents” given above.

A short circuit is an electrical circuit that allows a current to travelalong an unintended path, often where essentially no or a very lowelectrical impedance is encountered. In general, such short-circuitcurrents must be interrupted within less than 5 seconds after theiroccurrence and preferably quicker (e.g. within less than 3 seconds) toprevent damages in electrical networks.

According to the present invention, currents that flow from anelectrical network (in particular high-voltage network or medium-voltagenetwork) to ground via unintendend or intended paths and last longerthan 3 seconds or longer than 5 seconds, are considered “nonshort-circuit currents”. This definition of non-short-circuit currentsis based on their duration only and is independent of their magnitude orthe intendedness or unintendedness of their occurrence. In particular,this definition of non-short-circuit currents includes nominal currentsand excludes short-circuit currents of shorter than 5 seconds duration.

For example, such non-short-circuit currents can be currents that areinduced between two parallel overhead lines, wherein one line is on bothsides connected to ground and the other line is delivering current toloads. The non-short-circuit currents induced in the grounded overheadline can be interrupted by the devices according to the presentinvention.

Specifically, the device is a disconnector, in particular a high voltagedisconnector, or an earthing switch, in particular a make-proof earthingswitch.

According to a further aspect, the present invention also relates to alow voltage circuit breaker comprising at least two contacts movable inrelation to each other between a closed state and an open state anddefining an arcing region, in which an arc is generated during a currentinterrupting operation and in which an arc-quenching medium comprisingan organofluorine compound is present, wherein to the arcing region acounter-arcing component is allocated and is designed for counteractingthe generation of an arc and/or for supporting the extinction of an arc.

The present invention takes into account the surprising finding thatinspite of the high dielectric insulation performance of theorganofluorine compound, which is preferably used in combination with acarrier gas and more preferably with synthetic air or a gas mixturecontaining O₂ and CO₂, the cooling efficiency of an arc-quenching mediumcontaining an organofluorine compound is often insufficient forefficient arc extinction under free-burning conditions.

In contrast to conventional disconnectors, earthing switches or lowvoltage circuit breakers (low voltage shall typically be below few kVand in particular below 1 kV), in which the cooling efficiency of thearc extinction medium (e.g. SF₆) suffices to extinguish the arc underfree-burning conditions, the cooling insufficiency of the organofluorinecompound-containing arc-quenching medium is compensated for by thepresence of the counter-arcing component.

Consequently, potential arc extinction failures can reliably becircumvented also when using a non-SF₆ arc-quenching medium comprisingan organofluorine compound, which is favourable due to its environmentalfriendliness and low toxicity. Tus, the present invention allows usingthese non-SF₆ quenching media in devices for interrupting non-shortcircuit currents only and ensures a very safe operation of thesedevices.

It is understood that the embodiments described herein both relate tothe device for interrupting non-short circuit currents only,specifically to the disconnector or earthing switch, as well as to thelow voltage circuit breaker.

According to embodiments, the counter-arcing component comprises orconsists of an arc-cooling element for cooling the arc. In combinationwith the intrinsic cooling properties of the arc-quenching medium, acombined cooling effect is achieved that allows reliable currentinterruption.

According to further embodiments, the counter-arcing component isdesigned to be activated during a relative movement of the contacts fromclosed state to open state.

In particular embodiments, the counter-arcing component can comprise aflow-generating chamber, which is fluidically connected to the arcingregion by a flow channel and which is designed such that during arelative movement of the contacts from a closed state to an open state adifferential pressure is generated in the flow-generating chamber inrelation to the arcing region, said differential pressure causing a flowof the arc-quenching medium between the arcing region and theflow-generating chamber to take place. According to this embodiment, thearc-quenching medium is blown into the arcing region only when the arcis generated, i.e. when the contacts are under voltage and are movedrelative to each other from the closed state to the open state and forman arc in the arcing region between the contacts.

According to a very straightforward preferred design, at least one ofthe contacts forms a piston, which is slideably contained by a guidingtube forming a cylinder, the piston together with the cylinder defininga compression chamber as the flow-generating chamber, said compressionchamber being designed to be compressed during a relative movement ofthe contacts from a closed state to an open state. Specifically, therelative movement of the contacts is directly translated into a flow ofthe arc-quenching medium into the arcing region for extinction of thearc.

According to further embodiments, the connection between the arcingregion and the compression chamber is such that during compression, thearc-quenching medium contained in the compression chamber is ejectedinto the arcing region.

It is in this regard particularly preferred that the flow channel isformed axially within the piston. This allows for a very straightforwarddesign and further ensures that the distance, which has to be passed bythe arc-quenching medium from the compression chamber to the arcingregion, is kept as short as possible.

A particularly high blowing speed of the arc-quenching gas can beachieved, if a valve 44 is allocated to the flow channel, said valve 44opening when a threshold differential pressure is exceeded. Thedifferential pressure particularly relates to the pressure differencebetween the arcing region and the flow-generating chamber, in particularcompression chamber.

According to specific embodiments, the contact forming the piston is aplug contact designed to be slideably engaged within a tulip contact.

According to further specific embodiments, the contact forming thepiston is a tulip contact designed to engage around a plug contact. Inthis regard, the flow channel can be formed as a channel with circularcross-section running parallel to the axis of the tulip contact.

For example, the flow channel is in the form of a flow gap arrangedbetween the inner wall of the tulip contact and the outer wall of acylindrical flow guide which is radially enclosed by the tulip contactin a spaced-apart manner. The flow channel according to this embodimenthas in cross-section an annular form. More specifically, the inner wallof the tulip contact and the outer wall of a cylindrical flow guide runconcentrically and parallel to each other, in which case the flow gaphas a continuous cross-section over the axial length of the flow guide.More specifically, the flow guide can be formed as an insert fixed tothe tulip contact. The presence of a flow guide allows to guide (or“steer”) the flow of the arc-quenching medium in a manner such that aneven more efficient cooling of the arc is achieved.

Alternatively or additionally, the tulip contact is radially enclosed bya nozzle in a spaced-apart manner, thus forming a nozzle gap which opensout into the arcing region. The nozzle can in particular be a nozzlemade of polytetrafluorethylene (PTFE; Teflon®).

According to further embodiments, the contact forming the pistoncomprises a proximal contacting region and a distal compressing regionarranged axially opposite to the contacting region, wherein thecross-sectional area of the compressing region is larger than thecross-sectional area of the contacting region. By the compressing regionhaving a larger cross-sectional area, a higher pressure can be generatedin the compression chamber, allowing for a high blowing speed of thearc-quenching medium and thus a high cooling efficiency to be achieved.

According to still further embodiments, one of the contacts is in theform of a piston and is contained in the other contact, which forms acylinder for the piston, and the piston is slideably moveable in thecylinder in a gas-tight manner. Thereby, the piston and the cylindertogether form a suction chamber as the flow-generating chamber, saidsuction chamber being designed to increase in volume during a relativemovement of the contacts from a closed state to an open state. Thus,flow of the arc-quenching medium to be blown into the arcing region isaccording to this embodiment generated by suction.

In embodiments, the piston comprises in the region of its front endfacing the other contact an electrically insulating nose, specificallyin the form of an insulating plug. The insulating nose allows thedifferential pressure between the arcing region and the suction chamberto be further increased. Owing to the high differential pressure, veryhigh blowing speeds of the arc-quenching medium can be achieved. Inparticular regarding this embodiment, a high speed of contact movementor stroke shall be provided. For this purpose, a spring element ispreferably allocated to at least one moveable contact.

With regard to the above described embodiments, in which the piston andthe cylinder together form a suction chamber as the flow-generatingchamber, the device can preferably further comprise a control volumedesigned to be expanded during a relative movement of the contacts froma closed state to an open state, said control volume being in the openstate fluidically connected with the arcing region by at least one ventrunning through the wall of the cylinder. As the contact forming thecylinder, specifically the tulip contact, is pulled back, thearc-quenching medium is allowed to flow out through the vent; thebuilding up of pressure within the cylinder, which might counteract theflow of arc-quenching medium, can thus be avoided. It is therebyparticular preferred that the control volume is arranged radiallyoutside of the cylinder.

According to further embodiments, an ablating material, such as PTFE, isarranged adjacent to the contacts, the ablating material being designedto form ablation when exposed to an arc. When the arc is produced, itablates the ablating material, specifically PTFE, which leads toadditional pressure build-up in the arcing region. Without wanting to bebound by theory, it is further assumed that when the arc is produced,turbulence is created, which further cools the arc and hence enhancesarc extinction.

With regard to the above described embodiments, in which theflow-generating chamber is a compression chamber and a nozzle made ofablating material, in particular PTFE, is provided, the nozzle canfurther serve as a flow guide for guiding the arc-quenching medium tothe arcing region for optimal cooling.

With regard to the above described embodiments, in which theflow-generating chamber is a suction chamber and the ablating materialpreferably forms an electrically insulating nose, the arc burningdirectly over the insulating nose can generate additional over-pressureby material ablation, said over-pressure being proportional to thecurrent. If in addition a nozzle is present, the nozzle can be shaped toadjust the flow in the nozzle region, which can be of advantage to avoidexcessive pressure build up.

Additionally or alternatively, the device can comprise as acounter-arcing component a magnet generating a permanent magnetic fieldin the arcing region. This allows the arc to be moved or rotated andalso to be pushed out of the periphery, which causes longer arc lengthsand thus higher arc voltage drops and thereby improves extinction of thearc. In specific embodiments, the magnet generates a permanent magneticfield in the arcing region.

As also mentioned above, a spring element is preferably allocated to atleast one moveable contact. In specific embodiments, the contacts areheld off from transiting from a closed state to an open state by aholding force, and the spring element is designed to build up a springforce exceeding the holding force at a specific point in time. Inparticular, the one of the contacts can be in the form of a plug contacthaving a bulge, said bulge holding the plug contact off from axialmovement by a respective inward protrusion formed on the other contact,typically a tulip contact. When the spring force exceeds a thresholdvalue, the bulge forces the wall of the tulip contact towards an outwarddirection and thereby ultimately allows the plug contact to reboundaxially out of the tulip contact. Thus, the moving contact, specificallythe plug contact, is released at relatively high speed and furthercounteracts the generation of an arc and/or supports the extinction ofan arc during current interruption.

According to further embodiments, one of the contacts is in the form ofa piston and is contained in the other contact, which forms a cylinderfor the piston, and the piston is slideably moveable in the cylinder,wherein the piston comprises in the region of its front end facing theother contact a resistive element which in axial direction of the pistonis sandwiched between two regions of a material of lower resistance. Inthe closed state, the resistive element is in parallel with the regionsof lower resistance and, given that the resistance of the resistiveelement is much higher, the current flows through the regions of lowerresistance. When moving the contacts from the closed state to the openstate, the resistances of the resistive element and the regions of lowerresistance are in series and are dominated by the resistance of theresistive element. During the arc formation, the total resistance isthus approximately given by the sum of the resistances of the resistiveelement and the arc. During the opening process, the current in thecircuit is low because of the resistive element and hence the arcvoltage is increased (compared to without resistive element), which isfavourable for arc extinction.

The effect achieved by the present invention is of particular relevancein embodiments, in which the arc-quenching medium further comprises airor at least one air component, in particular selected from the groupconsisting of: oxygen (O₂) and nitrogen (N₂), carbon dioxide (CO₂), andmixtures thereof. The air or air component functions as a carrier gas orbackground gas additionally present to the organofluorine compound. Asdiscussed above, the present invention achieves safe operation of thedevice despite of the relatively poor cooling efficiency of the carriergas.

According to embodiments, the arc-quenching medium comprises carbondioxide and oxygen. It is thereby particularly preferred that the ratioof the amount of carbon dioxide to the amount of oxygen ranges from50:50 to 100:1. It is further preferred that the ratio of the amount ofcarbon dioxide to the amount of oxygen ranges from 80:20 to 95:5, morepreferably from 85:15 to 92:8, even more preferably from 87:13 to lessthan 90:10, and in particular is about 89:11. In this regard, it hasbeen found on the one hand that oxygen being present in a molar fractionof at least 5% allows soot formation to be prevented even after repeatedcurrent interruption events with relatively high current arcing. On theother hand, oxygen being present in a molar fraction of at most 20%(i.e. of 20% or less), more particularly of at most 15% (i.e. of 15% orless), reduces the risk of degradation of the material of the device byoxidation.

According to embodiments of the present invention, the organofluorinecompound is selected from the group consisting of fluoroethers(including oxiranes), in particular hydrofluoromonoethers,fluoroketones, in particular perfluoro-ketones, fluoroolefins, inparticular hydrofluoroolefins, fluoronitriles, in particularperfluoronitriles, and mixtures thereof.

In embodiments, the arc-quenching medium can comprise ahydrofluoromonoether containing at least three carbon atoms. A moredetailed description of such hydrofluoromonoethers is for example givenin WO 2012/080222, the disclosure of which is hereby incorporated byreference in its entirety.

In embodiments, the arc-quenching medium can comprise a fluoroketonecontaining from four to twelve carbon atoms, preferably containingexactly five carbon atoms or exactly six carbon atoms, or a mixturethereof. A more detailed description of such fluoroketones is forexample given in WO 2010/142346, the disclosure of which is herebyincorporated by reference in its entirety.

According to more specific embodiments, the fluoroketone is aperfluoroketone, and more particularly has the molecular formula C₅F₁₀O,i.e. it is fully saturated without any double or triple bonds betweencarbon atoms. The fluoroketone may more preferably be selected from thegroup consisting of:1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)butan-2-one (also nameddecafluoro-2-methylbutan-3-one),1,1,1,3,3,4,4,5,5,5-decafluoropentan-2-one,1,1,1,2,2,4,4,5,5,5-decafluoropentan-3-one and octafluorocylcopentanone,and most preferably is1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)butan-2-one.1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)butan-2-one can berepresented by the following structural formula (I):

1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)butan-2-one, herein brieflyreferred to as “C5K”, with molecular formula CF₃C(O)CF(CF₃)₂ or C₅F₁₀O,has been found to be particularly preferred for high and medium voltageinsulation applications, because it has the advantages of highdielectric insulation performance, in particular in mixtures with adielectric carrier gas, has very low GWP and has a low boiling point. Ithas an Ozone Depletion Potential (ODP) of 0 and is practicallynon-toxic.

Additionally or alternatively, the insulation medium can contain1,1,1,2,4,4,5,5,5-nonafluoro-2-(trifluoromethyl) pentan-3-one (alsonamed dodecafluoro-2-methylpentan-3-one), which can be represented bythe following structural formula (II):

1,1,1,2,4,4,5,5,5-Nonafluoro-4-(trifluoromethyl)pentan-3-one (herebriefly referred to as “C6K”) with molecular formula C₂F₅C(O)CF(CF₃)₂)has been found to be particularly preferred for high voltage insulationapplications because of its high insulating properties and its extremelylow GWP.

Specifically, its pressure-reduced breakdown field strength is around240 kV/(cm*bar), which is much higher than the one of air having a muchlower dielectric strength (E_(cr)=25 kV/(cm*bar)). It has an ozonedepletion potential of 0 and is non-toxic. Thus, the environmentalimpact is much lower than when using SF₆, and at the same timeoutstanding margins for human safety are achieved.

In additional or alternative embodiments, the arc-quenching mediumcomprises at least one compound being a hydrofluoro-ether selected fromthe group consisting of: hydrofluoro monoether containing at least threecarbon atoms; hydrofluoro monoether containing exactly three or exactlyfour carbon atoms; hydrofluoro monoether having a ratio of number offluorine atoms to total number of fluorine and hydrogen atoms of atleast 5:8; hydrofluoro monoether having a ratio of number of fluorineatoms to number of carbon atoms ranging from 1.5:1 to 2:1;pentafluoro-ethyl-methyl ether; 2,2,2-trifluoroethyl-trifluoromethylether; and mixtures thereof.

Additionally or alternatively, the arc-quenching medium can comprise afluoronitrile as organofluorine compound, in particular aperfluoronitrile. For example, the organofluorine compound can be afluoronitrile, specifically a perfluoronitrile, containing two carbonatoms, three carbon atoms or four carbon atoms. More particularly, thefluoronitrile can be a perfluoroalkylnitrile, specificallyperfluoroacetonitrile, perfluoropropionitrile (C₂F₅CN) and/orperfluorobutyronitrile (C₃F₇CN). Most particularly, the fluoronitrilecan be perfluoroisobutyronitrile (according to the formula (CF₃)₂CFCN)and/or perfluoro-2-methoxypropane-nitrile (according to the formulaCF₃CF(OCF₃)CN). Of these, perfluoroisobutyronitrile is particularlypreferred due to its low toxicity.

Additionally or alternatively, the arc-quenching medium can comprise afluoroolefin, in particular a hydrofluoroolefin. More particularly, thefluoroolefin or hydrofluorolefin, respectively, contains at least threecarbon atoms or contains exactly three carbon atoms. According toparticularly preferred embodiments, the hydrofluoroolefin is thusselected from the group consisting of: 1,1,1,2-tetrafluoropropene(HFO-1234yf; also named 2,3,3,3-tetrafluoro-1-propene),1,2,3,3-tetrafluoro-2-propene (HFO-1234yc),1,1,3,3-tetrafluoro-2-propene (HFO-1234zc),1,1,1,3-tetrafluoro-2-propene (HFO-1234ze),1,1,2,3-tetrafluoro-2-propene (HFO-1234ye), 1,1,1,2,3-pentafluoropropene(HFO-1225ye), 1,1,2,3,3-pentafluoropropene (HFO-1225yc),1,1,1,3,3-pentafluoropropene (HFO-1225zc), (Z)1,1,1,3-tetrafluoropropene(HFO-1234zeZ); also named cis-1,3,3,3-tetrafluoro-1-propene),(Z)1,1,2,3-tetrafluoro-2-propene (HFO-1234yeZ),(E)1,1,1,3-tetrafluoropropene (HFO-1234zeE; also namedtrans-1,3,3,3-tetrafluoro-1-propene), (E)1,1,2,3-tetrafluoro-2-propene(HFO-1234yeE), (Z)1,1,1,2,3-pentafluoropropene (HFO-1225yeZ; also namedcis-1,2,3,3,3 pentafluoroprop-1-ene), (E)1,1,1,2,3-pentafluoropropene(HFO-1225yeE; also named trans-1,2,3,3,3 pentafluoroprop-1-ene), andmixtures thereof.

In embodiments, the device of the present invention can in particular bea high voltage disconnector. More particular, it can be a high voltagedisconnector designed for bus charging, in particular rated for acurrent in the range from 0.1 A to 0.8 A and a voltage in the range from72.5 kV to 800 kV. Higher ratings may be addressed in the future, aswell.

In addition or alternatively, the device can be an earthing switch for ahigh voltage disconnector, which high voltage disconnector is designedfor induced current switching, and in particular is rated for a currentof 200 A at most and a voltage of 32 kV at most. Higher ratings may beaddressed in the future, as well.

Alternatively, it can be a high voltage disconnector designed for bustransfer switching, and in particular is rated for a current of 1.6 kAat most and a voltage in the range from 10 V to 40 V. Higher ratings maybe addressed in the future, as well.

Disconnectors of this type using SF₆ as arc-quenching medium are knownin the art, but do not comprise any counter-arcing component accordingto the present invention. Counter-arcing components are nowheresuggested in the art, since the arc cooling properties of thearc-quenching gas is generally considered sufficient for extinguishingthe arc under unblown conditions.

According to a further aspect, the present invention also relates to amedium voltage or high voltage gas-insulated switchgear comprising adevice as described above.

The present invention is further illustrated by way of the attachedfigures, of which:

FIG. 1a, 1b show schematically a counter-arcing component of a firstembodiment of the device, the counter-arcing component being activatedduring a relative movement of the contacts from a closed state shown inFIG. 1a to an open state shown in FIG. 1 b;

FIG. 2a, 2b show schematically a counter-arcing component of a secondembodiment of the device, the counter-arcing component being activatedduring a relative movement of the contacts from a closed state shown inFIG. 2a to an open state shown in FIG. 2 b;

FIG. 3a, 3b show schematically a counter-arcing component of a thirdembodiment of the device, the counter-arcing component being activatedduring a relative movement of the contacts from a closed state shown inFIG. 3a to an open state shown in FIG. 3b ; and

FIG. 4 shows schematically two contacts of an exemplary device with aspring element being allocated to one of the contacts.

As shown exemplarily in FIG. 1, the device of the present inventioncomprises two contacts 10, 12 movable in relation to each other,specifically a first contact 10 in the form of a tulip contact 101,which in the closed position engages around second contact 12 in theform of a plug contact 121.

The tulip contact 101 is slideably contained in a guiding tube 14forming a cylinder 16 having a continuous inner wall 18. Thus, the tulipcontact 101 forms a piston 20, which together with the cylinder 16defines a compression chamber 22 containing arc-quenching medium 17.Within the piston 20, a flow channel 24 is formed running in axiallythrough the center of the piston 20.

During the movement of the tulip contact 101 from the closed state shownin FIG. 1a to the open state shown in FIG. 1b , the compression chamber22 is compressed by the piston 20, which moves in direction shown by thearrow in FIG. 1b , and the arc-quenching medium 17 contained in thecompression chamber 22 is forced through the flow channel 24 fluidicallyconnecting the compression chamber 22 with the arcing region 26. Thus,arc-extinction medium is ejected into the arcing region 26 at arelatively high blowing speed, which supports extinction of the arc 27.

In other words, a differential pressure between the compression chamber22 and the arcing region 26 is generated by slideably moving the piston20 within the guiding tube 14 and hence compressing the compressionchamber 22. This causes a flow of the arc-quenching medium 17 from thecompression chamber 22 functioning as a flow-generating chamber 21 tothe arcing region 26.

The embodiment according to FIG. 1a, 1b thus comprises a counter-arcingcomponent 19, which comprises a flow-generating chamber 21, in which theflow is generated by compression. Since by increasing the blowing speed,the arc is efficiently cooled, the counter-arcing component functions inthis embodiment as an arc-cooling element.

According to the embodiment shown in FIG. 2a, 2b , a first contact 10′is in the form of a tulip contact 101′ in which the second contact 12′in the form of a plug contact 121′ is contained. The tulip contact 101′forms a cylinder 16′ in which the plug contact 121′ forming a piston 20′is slideably moveable in a gas-tight manner. Thus, the piston 20′ andthe cylinder 16′ together form a suction chamber 28 functioning as aflow-generating chamber 21′.

In the region of its front end facing the tulip contact 101′, the piston20′ can in particular comprise an electrically insulating nose 30.

During relative movement of the contacts 10′, 12′ from a closed stateshown in FIG. 2a to an open state shown in FIG. 2b , the volume of thesuction chamber 28 is increased. At a certain point in the movement, thecontacts 10′, 12′ become separated and the current is interrupted, butthe insulating nose 30 of the piston 20′ still remains at least to acertain part inside the suction chamber 28. By further moving the piston20′ in the direction away from the cylinder 16′, the differentialpressure is further increased, owing to the insulating nose 30functioning as a plug prohibiting pressure equalization. In this state,the arc 27 burns directly over the insulating nose 30, wherebyadditional over-pressure is generated by material ablation, whichfurther contributes to an even higher differential pressure between thearcing region 26 and the suction chamber 28. At the moment, when theinsulating nose 30 is finally released from the cylinder 16′, thearc-quenching medium 17 thus flows into the suction chamber 28 at a veryhigh flowing speed generated by the high differential pressure.Ultimately, a strong blowing effect is achieved by the arc-quenchingmedium 17 flowing at high speed across the arcing region 26, andextinction of the arc 27 is thereby supported.

Similarly to the embodiment shown in FIG. 2a, 2b , also the embodimentshown in FIG. 3a, 3b comprises a first contact 10″ in the form of atulip contact 101″ forming a cylinder 16″, in which a second contact 12″in the form of a plug contact 121″ forming a piston 20″ is slideablymoveable in a gas-tight manner. Also in this embodiment, the piston 20″and the cylinder 16″ together form a suction chamber 28″, whichfunctions as a flow-generating chamber 21″.

In distinction to the embodiment shown in FIG. 2a, 2b , the piston 20″of FIG. 3a, 3b comprises in the region of its front end facing the tulipcontact 101″ a resistive element 32 which in axial direction of thepiston 20″ is sandwiched between two regions 34 a, 34 b of alower-resistance material.

In the closed state, the resistive element 32 is in parallel with theregions 34 a, 34 b of lower resistance, as schematically shown on theright hand side of FIG. 3a . As the resistance of resistive element 32is much higher, the current flows through the lower-resistance regions34 a, 34 b.

When moving the contacts 10″, 12″ from the closed state shown in FIG. 3ato the open state shown in FIG. 3b , the resistances R_(M) and R_(M) ofthe lower-resistance regions 34 a, 34 b and R_(R) of the resistiveelement 32 get to be in series, as schematically shown on the right handside of FIG. 3b , and are thus dominated by the resistance R_(R) of theresistive element 32. During formation of the arc 27, the totalresistance is thus given (in good approximation) by the sum of theresistances R_(R) of the resistive element 32 and R_(arc) of the arc 27.During the opening process, the current in this current path is lowbecause of the resistive element 32, and hence the arc voltage drop maybecome higher than it would be without resistive element 32, whichfavourably supports arc extinction.

The blowing effect achieved by the device of the present invention, inparticular of the embodiments shown above, can further be increased by aspring element as shown in FIG. 4. Therein, a first contact 10′″ is inthe form of a tulip contact 101′″, whereas the second contact 12′″ is inthe form of a plug contact 121′″, as for the embodiments shown above.However, in the embodiment of FIG. 4, the plug contact 121′″ has a bulge38, which holds the plug contact 121′″ off from axial movement away fromthe tulip contact 101′″. To this end, a respective inward protrusion 40is formed on the inside area 42 of the tulip contact 101′″.

When pulling the contacts 10′″, 12′″ in a direction away from eachother, a point is achieved when the spring force 36 or pulling force 36exceeds the holding force between the contacts 10′″ or 101′″ and 12″ or121′″, respectively. At this point, the bulge 38 forces the wall 41 ofthe tulip contact 101′″ in an outward direction, ultimately allowing theplug contact 121′″ to rebound axially out of the tulip contact 101′″.Thus, the plug contact 121′″ is released at relatively high speed andfurther counteracts the generation of the arc and/or supports theextinction of the arc during current interruption.

LIST OF REFERENCE NUMERALS

-   10, 101; 10′, 101′; 10″, 101″; 10′″, 101′″ first contact, tulip    contact-   12, 121; 12′, 121′; 12″, 121″; 12′″, 121′″ second contact, plug    contact-   14 guiding tube-   16, 16′, 16″ cylinder-   17 arc-quenching medium-   18 inner wall of cylinder-   19 counter-arcing component-   20, 20′, 20″ piston-   21, 21′, 21″ flow-generating chamber-   22 compression chamber-   24 flow channel-   26 arcing region-   27 arc-   28, 28″ suction chamber-   30 electrically insulating nose-   32 resistive element of resistance value R_(R)-   34 a, 34 b regions of piston made of material of lower resistance    values R_(M)-   36 spring element-   38 bulge-   40 inward protrusion-   41 wall of the tulip contact-   42 inside area of tulip contact-   44 flow channel valve

1-37. (canceled)
 38. A device for interrupting non-short-circuitcurrents only, the device comprising: at least two contacts movable inrelation to each other between a closed state and an open state anddefining an arcing region, in which an arc is generated during a currentinterrupting operation and in which an arc-quenching medium comprisingan organofluorine compound is present, wherein a counter-arcingcomponent is allocated to the arcing region and is designed forcounteracting the generation of the arc and/or is designed forsupporting extinction of the arc, wherein one of the contacts is in theform of a piston contained by the other contact forming a cylinder andbeing slideably moveable in the cylinder, the piston comprising in theregion of its front end facing the other contact a resistive elementwhich in axial direction of the piston is sandwiched between two regionsof a material of lower resistance.
 39. The device according to claim 38,wherein the arc-quenching medium further comprises air or at least oneair component.
 40. The device according to claim 39, wherein thearc-quenching medium comprises a mixture of carbon dioxide and oxygen.41. The device according to claim 40, wherein the ratio of the amount ofcarbon dioxide to the amount of oxygen ranges from 50:50 to 100:1. 42.The device according to claim 38, wherein the organofluorine compound isselected from the group consisting of: fluoroethers, fluoroolefins, andfluoronitriles, and mixtures thereof.
 43. The device according to claim38, wherein the arc-quenching medium comprises a fluoroketone containingfrom four to twelve carbon atoms.
 44. The device according to claim 38,wherein the arc-quenching medium comprises a hydrofluoromonoethercontaining at least three carbon atoms.
 45. The device according toclaim 38, wherein the device is a high voltage disconnector designed forbus charging, in particular rated for a current in the range from 0.1 Ato 0.8 A and a voltage in the range from 72.5 kV to 800 kV.
 46. Thedevice according to claim 38, wherein the device is an earthing switchof a high voltage disconnector designed for induced current switching.47. The device according to claim 38, wherein the device is a highvoltage disconnector designed for bus transfer switching.
 48. The deviceaccording to claim 38, wherein the device is different from a circuitbreaker, which circuit breaker is capable of interrupting short-circuitcurrents; and/or the device is unable to interrupt short-circuitcurrents.
 49. The device according to claim 38, wherein the devicecomprising means for interrupting the non-short-circuit currents; and/orthe device does not have means for interrupting short-circuit currents.50. The device according to claim 38, wherein the non-short-circuitcurrents are currents that flow from an electrical network to ground viaunintended or intended paths and last longer than 3 seconds.
 51. Amedium voltage or high voltage gas-insulated switchgear comprising adevice according to claim 38.